The present invention relates to a communication system formed of an MPLS network and a modified ATM network. More specifically, the present invention relates to a communication system formed of an MPLS network and a modified ATM network where an MPLS packet has a first label which directs the MPLS packet to a switch in the network and a second label which directs the MPLS packet to an output port in a switch.
The multiprotocol label switching (MPLS) standard is being pushed within the IETF by large ISP networks (UUNet primarily) and by several networking companies, including Cisco and Juniper Networks.
The ISP network topology of primary concern is a core of ATM switches surrounded by IP routers. The ATM switches provide a mesh of connections between the routers where every router has at least one VC between itself and every other router. The virtual circuits between the routers are xe2x80x9cengineeredxe2x80x9d by the ISP operations team to provide load balancing, efficient usage of the network resources and resilience to link and node failures.
The stability of the core ISP network is of utmost importance to the ISP operations team. ISPs want their core networks to be extremely stable and resilient. They are risk-adverse in this portion of the network, and tend to prefer simple solutions with well-understood failure modes over complicated solutions with unknown or unpredictable failure modes. For example, the mesh of VCCs connecting the routers of internetMCI (now Cable and Wireless) are PVCs. The backup VCCs between routers were PVCs as well, but recently have been converted over to SPVCs (with designated transit lists).
The IP+ATM network architecture has two primary problems, the first being the ability of the network to scale, and the second being the ability of the network to support new types of packet services,
The IP+ATM network architecture cannot grow indefinitely for two reasons. The first is that the number of virtual circuits required to connect all the routers together is on the order of N{circumflex over ( )}2 in the number of routers. With 512k connections supported on an ASX-4000, this limits the size of the network to approximately 700 routers (assuming all the connections go through a single ASX-4000 at some point). The second and more serious issue limiting growth is the IP routing protocols themselves. Every router connected to the ATM core is xe2x80x9cadjacentxe2x80x9d to every other router. For a link-state routing protocol like OSPF, each router has to maintain separate state for the routers it is directly connected to, and all network topology changes seen by one router must be flooded to every adjacent router. Maintaining a large number of adjacencies and processing the topology updates can be very CPU intensive in a large networkxe2x80x94processing the flooding messages alone is on the order of N{circumflex over ( )}3 in the number of routers. The IP routing protocols simply were not designed for a large number of adjacencies; the common rule of thumb for OSPF is that an OSPF area is limited to approximately 200 routers.
VC Merge is one possible solution to the N{circumflex over ( )}2 connection space problem. (Recall that VC Merge is an AAL5 connection where an ATM switch merges multiple incoming connections onto the same outgoing virtual circuit.) VC Merge replaces the N{circumflex over ( )}2 mesh of point-to-point virtual circuits with N multi-point to point trees, where each router is at the receiving end of one of the trees, and a possible sender for the remaining Nxe2x88x921 trees.
While VC Merge addresses the connection space issue, it does not address the router adjacency issue. No general solution for this problem is currently known.
Today""s Internet is a best-effort packet delivery service where everyone gets the same level of service. ISPs would like to provide more profitable services than best-effort, in order to differentiate their offerings from other ISPs. Two potential service offerings that have momentum within the IEFT Differentiated Services working group are the Virtual Leased Line Service (VLL) and the Assured Forwarding Service (AF). The VLL service is a CBR-like service, while AF-is VBR-like. For the ISP, providing these services means mapping the customer-desired end-to-end behavior onto their network where they have two different control planes, ATM and IP, and two different QOS treatments, ATM strict QOS, and the emerging IP differentiated services QOS, which can be thought of as xe2x80x9cloosexe2x80x9d QOS.
The present invention solves the above two issues by combining the best of the IP and connection-oriented worlds.
The present invention pertains to a communication system. The system comprises an MPLS network. The system comprises a modified ATM network connected to the MPLS network on which MPLS packets can travel.
The present invention pertains to a switch for switching MPLS packets and ATM cells in a network. The switch comprises input ports for receiving MPLS packets and ATM cells from the network. Each MPLS packet has a first label for directing the packet to a desired switch and a second label for directing the packet in the switch to a desired output port in the switch. The system comprises output ports for sending MPLS packets and ATM cells to the network. The system comprises a mechanism for reviewing the second label of the packet while maintaining the first label with the packet. The reviewing mechanism is connected to the input ports and the output ports.
The present invention pertains to a method for transmitting packets in a communications network. The method comprises the steps of sending an MPLS packet on an MPLS network to a first switch connected to a modified ATM network and the MPLS network. Then there is the step of transferring the MPLS packet to a second switch of the ATM network with the first switch through the ATM network.